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Do not covariantly mix in constraints from contravarrying positions #43439

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Merged
weswigham merged 4 commits into from
Apr 5, 2021
Merged

Do not covariantly mix in constraints from contravarrying positions #43439

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cb1833b
Do not covariantly mix in constraints from contravarrying positions
weswigham Mar 30, 2021
a7352e6
Exclude keyof from constraint variance tracking
weswigham Mar 30, 2021
6abbc96
Extra test case
weswigham Mar 30, 2021
c392b0f
Always subtitute on type parameter types
weswigham Apr 1, 2021
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10 changes: 9 additions & 1 deletion 10 src/compiler/checker.ts
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Expand Up @@ -12849,9 +12849,17 @@ namespace ts {

function getConditionalFlowTypeOfType(type: Type, node: Node) {
let constraints: Type[] | undefined;
let covariant = true;
while (node && !isStatement(node) && node.kind !== SyntaxKind.JSDocComment) {
const parent = node.parent;
if (parent.kind === SyntaxKind.ConditionalType && node === (<ConditionalTypeNode>parent).trueType) {
// only consider variance flipped by parameter locations - `keyof` types would usually be considered variance inverting, but
// often get used in indexed accesses where they behave sortof invariantly, but our checking is lax
if (parent.kind === SyntaxKind.Parameter) {
covariant = !covariant;
}
// Always substitute on type parameters, regardless of variance, since even
// in contravarrying positions, they may be reliant on subtuted constraints to be valid
if ((covariant || type.flags & TypeFlags.TypeParameter) && parent.kind === SyntaxKind.ConditionalType && node === (<ConditionalTypeNode>parent).trueType) {
const constraint = getImpliedConstraint(type, (<ConditionalTypeNode>parent).checkType, (<ConditionalTypeNode>parent).extendsType);
if (constraint) {
constraints = append(constraints, constraint);
Expand Down
53 changes: 53 additions & 0 deletions 53 tests/baselines/reference/callOfConditionalTypeWithConcreteBranches.js
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//// [callOfConditionalTypeWithConcreteBranches.ts]
type Q<T> = number extends T ? (n: number) => void : never;
function fn<T>(arg: Q<T>) {
// Expected: OK
// Actual: Cannot convert 10 to number & T
arg(10);
}
// Legal invocations are not problematic
fn<string | number>(m => m.toFixed());
fn<number>(m => m.toFixed());

// Ensure the following real-world example that relies on substitution still works
type ExtractParameters<T> = "parameters" extends keyof T
// The above allows "parameters" to index `T` since all later
// instances are actually implicitly `"parameters" & keyof T`
? {
[K in keyof T["parameters"]]: T["parameters"][K];
}[keyof T["parameters"]]
: {};

// Original example, but with inverted variance
type Q2<T> = number extends T ? (cb: (n: number) => void) => void : never;
function fn2<T>(arg: Q2<T>) {
function useT(_arg: T): void {}
// Expected: OK
arg(arg => useT(arg));
}
// Legal invocations are not problematic
fn2<string | number>(m => m(42));
fn2<number>(m => m(42));

// webidl-conversions example where substituion must occur, despite contravariance of the position
// due to the invariant usage in `Parameters`

type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void : Function;

//// [callOfConditionalTypeWithConcreteBranches.js]
function fn(arg) {
// Expected: OK
// Actual: Cannot convert 10 to number & T
arg(10);
}
// Legal invocations are not problematic
fn(function (m) { return m.toFixed(); });
fn(function (m) { return m.toFixed(); });
function fn2(arg) {
function useT(_arg) { }
// Expected: OK
arg(function (arg) { return useT(arg); });
}
// Legal invocations are not problematic
fn2(function (m) { return m(42); });
fn2(function (m) { return m(42); });
105 changes: 105 additions & 0 deletions 105 tests/baselines/reference/callOfConditionalTypeWithConcreteBranches.symbols
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=== tests/cases/compiler/callOfConditionalTypeWithConcreteBranches.ts ===
type Q<T> = number extends T ? (n: number) => void : never;
>Q : Symbol(Q, Decl(callOfConditionalTypeWithConcreteBranches.ts, 0, 0))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 0, 7))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 0, 7))
>n : Symbol(n, Decl(callOfConditionalTypeWithConcreteBranches.ts, 0, 32))

function fn<T>(arg: Q<T>) {
>fn : Symbol(fn, Decl(callOfConditionalTypeWithConcreteBranches.ts, 0, 59))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 1, 12))
>arg : Symbol(arg, Decl(callOfConditionalTypeWithConcreteBranches.ts, 1, 15))
>Q : Symbol(Q, Decl(callOfConditionalTypeWithConcreteBranches.ts, 0, 0))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 1, 12))

// Expected: OK
// Actual: Cannot convert 10 to number & T
arg(10);
>arg : Symbol(arg, Decl(callOfConditionalTypeWithConcreteBranches.ts, 1, 15))
}
// Legal invocations are not problematic
fn<string | number>(m => m.toFixed());
>fn : Symbol(fn, Decl(callOfConditionalTypeWithConcreteBranches.ts, 0, 59))
>m : Symbol(m, Decl(callOfConditionalTypeWithConcreteBranches.ts, 7, 20))
>m.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
>m : Symbol(m, Decl(callOfConditionalTypeWithConcreteBranches.ts, 7, 20))
>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))

fn<number>(m => m.toFixed());
>fn : Symbol(fn, Decl(callOfConditionalTypeWithConcreteBranches.ts, 0, 59))
>m : Symbol(m, Decl(callOfConditionalTypeWithConcreteBranches.ts, 8, 11))
>m.toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))
>m : Symbol(m, Decl(callOfConditionalTypeWithConcreteBranches.ts, 8, 11))
>toFixed : Symbol(Number.toFixed, Decl(lib.es5.d.ts, --, --))

// Ensure the following real-world example that relies on substitution still works
type ExtractParameters<T> = "parameters" extends keyof T
>ExtractParameters : Symbol(ExtractParameters, Decl(callOfConditionalTypeWithConcreteBranches.ts, 8, 29))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 11, 23))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 11, 23))

// The above allows "parameters" to index `T` since all later
// instances are actually implicitly `"parameters" & keyof T`
? {
[K in keyof T["parameters"]]: T["parameters"][K];
>K : Symbol(K, Decl(callOfConditionalTypeWithConcreteBranches.ts, 15, 9))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 11, 23))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 11, 23))
>K : Symbol(K, Decl(callOfConditionalTypeWithConcreteBranches.ts, 15, 9))

}[keyof T["parameters"]]
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 11, 23))

: {};

// Original example, but with inverted variance
type Q2<T> = number extends T ? (cb: (n: number) => void) => void : never;
>Q2 : Symbol(Q2, Decl(callOfConditionalTypeWithConcreteBranches.ts, 17, 7))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 20, 8))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 20, 8))
>cb : Symbol(cb, Decl(callOfConditionalTypeWithConcreteBranches.ts, 20, 33))
>n : Symbol(n, Decl(callOfConditionalTypeWithConcreteBranches.ts, 20, 38))

function fn2<T>(arg: Q2<T>) {
>fn2 : Symbol(fn2, Decl(callOfConditionalTypeWithConcreteBranches.ts, 20, 74))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 21, 13))
>arg : Symbol(arg, Decl(callOfConditionalTypeWithConcreteBranches.ts, 21, 16))
>Q2 : Symbol(Q2, Decl(callOfConditionalTypeWithConcreteBranches.ts, 17, 7))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 21, 13))

function useT(_arg: T): void {}
>useT : Symbol(useT, Decl(callOfConditionalTypeWithConcreteBranches.ts, 21, 29))
>_arg : Symbol(_arg, Decl(callOfConditionalTypeWithConcreteBranches.ts, 22, 16))
>T : Symbol(T, Decl(callOfConditionalTypeWithConcreteBranches.ts, 21, 13))

// Expected: OK
arg(arg => useT(arg));
>arg : Symbol(arg, Decl(callOfConditionalTypeWithConcreteBranches.ts, 21, 16))
>arg : Symbol(arg, Decl(callOfConditionalTypeWithConcreteBranches.ts, 24, 6))
>useT : Symbol(useT, Decl(callOfConditionalTypeWithConcreteBranches.ts, 21, 29))
>arg : Symbol(arg, Decl(callOfConditionalTypeWithConcreteBranches.ts, 24, 6))
}
// Legal invocations are not problematic
fn2<string | number>(m => m(42));
>fn2 : Symbol(fn2, Decl(callOfConditionalTypeWithConcreteBranches.ts, 20, 74))
>m : Symbol(m, Decl(callOfConditionalTypeWithConcreteBranches.ts, 27, 21))
>m : Symbol(m, Decl(callOfConditionalTypeWithConcreteBranches.ts, 27, 21))

fn2<number>(m => m(42));
>fn2 : Symbol(fn2, Decl(callOfConditionalTypeWithConcreteBranches.ts, 20, 74))
>m : Symbol(m, Decl(callOfConditionalTypeWithConcreteBranches.ts, 28, 12))
>m : Symbol(m, Decl(callOfConditionalTypeWithConcreteBranches.ts, 28, 12))

// webidl-conversions example where substituion must occur, despite contravariance of the position
// due to the invariant usage in `Parameters`

type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void : Function;
>X : Symbol(X, Decl(callOfConditionalTypeWithConcreteBranches.ts, 28, 24))
>V : Symbol(V, Decl(callOfConditionalTypeWithConcreteBranches.ts, 33, 7))
>V : Symbol(V, Decl(callOfConditionalTypeWithConcreteBranches.ts, 33, 7))
>args : Symbol(args, Decl(callOfConditionalTypeWithConcreteBranches.ts, 33, 23))
>args : Symbol(args, Decl(callOfConditionalTypeWithConcreteBranches.ts, 33, 49))
>Parameters : Symbol(Parameters, Decl(lib.es5.d.ts, --, --))
>V : Symbol(V, Decl(callOfConditionalTypeWithConcreteBranches.ts, 33, 7))
>Function : Symbol(Function, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

99 changes: 99 additions & 0 deletions 99 tests/baselines/reference/callOfConditionalTypeWithConcreteBranches.types
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=== tests/cases/compiler/callOfConditionalTypeWithConcreteBranches.ts ===
type Q<T> = number extends T ? (n: number) => void : never;
>Q : Q<T>
>n : number

function fn<T>(arg: Q<T>) {
>fn : <T>(arg: Q<T>) => void
>arg : Q<T>

// Expected: OK
// Actual: Cannot convert 10 to number & T
arg(10);
>arg(10) : void
>arg : Q<T>
>10 : 10
}
// Legal invocations are not problematic
fn<string | number>(m => m.toFixed());
>fn<string | number>(m => m.toFixed()) : void
>fn : <T>(arg: Q<T>) => void
>m => m.toFixed() : (m: number) => string
>m : number
>m.toFixed() : string
>m.toFixed : (fractionDigits?: number) => string
>m : number
>toFixed : (fractionDigits?: number) => string

fn<number>(m => m.toFixed());
>fn<number>(m => m.toFixed()) : void
>fn : <T>(arg: Q<T>) => void
>m => m.toFixed() : (m: number) => string
>m : number
>m.toFixed() : string
>m.toFixed : (fractionDigits?: number) => string
>m : number
>toFixed : (fractionDigits?: number) => string

// Ensure the following real-world example that relies on substitution still works
type ExtractParameters<T> = "parameters" extends keyof T
>ExtractParameters : ExtractParameters<T>

// The above allows "parameters" to index `T` since all later
// instances are actually implicitly `"parameters" & keyof T`
? {
[K in keyof T["parameters"]]: T["parameters"][K];
}[keyof T["parameters"]]
: {};

// Original example, but with inverted variance
type Q2<T> = number extends T ? (cb: (n: number) => void) => void : never;
>Q2 : Q2<T>
>cb : (n: number) => void
>n : number

function fn2<T>(arg: Q2<T>) {
>fn2 : <T>(arg: Q2<T>) => void
>arg : Q2<T>

function useT(_arg: T): void {}
>useT : (_arg: T) => void
>_arg : T

// Expected: OK
arg(arg => useT(arg));
>arg(arg => useT(arg)) : void
>arg : Q2<T>
>arg => useT(arg) : (arg: T & number) => void
>arg : T & number
>useT(arg) : void
>useT : (_arg: T) => void
>arg : T & number
}
// Legal invocations are not problematic
fn2<string | number>(m => m(42));
>fn2<string | number>(m => m(42)) : void
>fn2 : <T>(arg: Q2<T>) => void
>m => m(42) : (m: (n: number) => void) => void
>m : (n: number) => void
>m(42) : void
>m : (n: number) => void
>42 : 42

fn2<number>(m => m(42));
>fn2<number>(m => m(42)) : void
>fn2 : <T>(arg: Q2<T>) => void
>m => m(42) : (m: (n: number) => void) => void
>m : (n: number) => void
>m(42) : void
>m : (n: number) => void
>42 : 42

// webidl-conversions example where substituion must occur, despite contravariance of the position
// due to the invariant usage in `Parameters`

type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void : Function;
>X : X<V>
>args : any[]
>args : Parameters<V>

34 changes: 34 additions & 0 deletions 34 tests/cases/compiler/callOfConditionalTypeWithConcreteBranches.ts
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@@ -0,0 +1,34 @@
type Q<T> = number extends T ? (n: number) => void : never;
function fn<T>(arg: Q<T>) {
// Expected: OK
// Actual: Cannot convert 10 to number & T
arg(10);
}
// Legal invocations are not problematic
fn<string | number>(m => m.toFixed());
fn<number>(m => m.toFixed());

// Ensure the following real-world example that relies on substitution still works
type ExtractParameters<T> = "parameters" extends keyof T
// The above allows "parameters" to index `T` since all later
// instances are actually implicitly `"parameters" & keyof T`
? {
[K in keyof T["parameters"]]: T["parameters"][K];
}[keyof T["parameters"]]
: {};

// Original example, but with inverted variance
type Q2<T> = number extends T ? (cb: (n: number) => void) => void : never;
function fn2<T>(arg: Q2<T>) {
function useT(_arg: T): void {}
// Expected: OK
arg(arg => useT(arg));
}
// Legal invocations are not problematic
fn2<string | number>(m => m(42));
fn2<number>(m => m(42));

// webidl-conversions example where substituion must occur, despite contravariance of the position
// due to the invariant usage in `Parameters`

type X<V> = V extends (...args: any[]) => any ? (...args: Parameters<V>) => void : Function;
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